Device for moulding sintering blanks

ABSTRACT

A device for moulding blanks with undercut parts to be sintered by compaction of powdered material. A two part die forms the chamber in which the blank is moulded. A pair of opposed punches pass through the die to compact the powdered material. The two parts of the die are held firmly in contact with one another during the stroke of the punches by an annular collar with inclined surface engaging oppositely inclined surfaces on the die. After the material has been compacted, the two parts of the die are separated in such a direction as not to interfere with the undercut portions of the blanks. After the die has opened, one of the punches retracts while the other continues its stroke to move the blank from between the two parts of the die.

United States Patent [1 1 Viadana 3,752,622 1451 Aug. 14, 1973 X XX U/44EH55 5435 a max m H M m m 2 4 m w a m w m ow mmd m SB&M 36 2 2256 9999mmwm nwww .9 mm Mm b. 23 y G m I m a m n O m m m S C G 1 N a I D m L I WW M m m an 8 wk m I N m VAe EL m DB1 M U 5 U [73] Assignee: lng. C.Olivetti & C., S.p.A., lvera,

Torino, Italy Primary Examiner-R0bert L. Spicer, Jr. Attorney-Birch eta1.

[22] Filed: Sept. 21, 1971 [21] Appl. No.: 182,352

[5 7] ABSTRACT A device for moulding blanks with undercut parts to be[30] Foreign Application Priority Data sintered by compaction ofpowdered material. A two Sept. 22, 1970 P die ffms the chamber in whichblank is moulded. A pair of opposed punches pass through the die tocompact the powdered material. The two of the die are held firmly incontact with one an parts other 425/444, 425/450, 425/DIG. 35, 425/DIG.58 Int. Cl. [58] Field of Search............-....

during the stroke of the punches by an annular collar B29c 7/00, B2903/00 with inclined surface engaging oppositely inclined surfaces on thedie. After the material has been corn- 425/330, 411, 438, 444, 450, 804,DIG. 35,

pacted, the two parts of the die are separated in such DIG. 58

a direction as not to interfere with the undercut por- [56] ReferencesCited tions of the blanks. After the die has opened, one of the punchesretracts while the other continues its stroke to UNITED STATES PATENTSmove the blank from between the two parts of the die. 2,482,342 9/1949Hubbert et 425/78 2,360 528 10/1944 Talmage................ 425mm. 58 UX10 Claims, 12 Drawing Figures Patented Aug. 14, 1973 .7 Sheets-Sheet 1FIG 2 FIG. 8

FIG. 3

Patented Aug. 14, 1973 .7 Sheets-Sheet- I FIG. 5

Patented Aug. 14, 1973 ,7 Sheets-Sheet 5 FIG. 6

Patented Aug. 14, 1973 .7 Sheets-Sheet 4 FIG. 10

Patented Aug. 14, 1973 .7 Sheets-Sheet 5 FIG. 9

Patented Aug. 14, 1973 .7 Sheets-Sheet 6 FIG. 11

Patented Aug. 14, 1973 7 Sheets-Sheet '7 aid 'IIIIIIIIIIIIIIIIII/ A m MFIG. 12

DEVICE FOR MOULDING SINTERING BLANKS BACKGROUND OF THE INVENTION Thisinvention relates to a device for moulding blanks to be sintered and issuitable for moulding blanks with undercut parts which prevent removalof the blanks from the dies by axial displacement. For instance, thedevice may be used for moulding blanks with a least one central partwhose cross section, perpendicular to the axis, is smaller than thecross sections of both adjacent parts.

The prior art shows a device for moulding blanks to be sintered whichcomprises two cylindrical and/or prismatic parts of different crosssection, united in correspondence with a horizontal plane which isperpendicular to the direction of their longitudinal axis. This deviceessentially comprises a pair of punches movable one towards the other ina direction perpendicular to the aforementioned plane and an assembly oftwo adjacent dies, normally in contact with one another, each of whichis associated with one of the punches and is adapted for moulding one ofthe parts. The axes of the punches and the dies mentioned above arevertical and thepowdered material is fed to the upper die when the punchassociated therewith is lifted from the die. Suitable means are providedfor moving the punches one towards the other in order to compact thepowdered material and to form the blank. One of the two dies is axiallymovable relative to the other in a direction perpendicular to the saidplane with a stroke which is at least equal to the height of the blank.During the stroke, a portion of the blank is removed from one of thedies; further, the punch associated with the other die is axiallymovable relative to the latter with a stroke which is at least equal tothe height of the remaining part of the blank in order to remove thispart from the corresponding die.

The device of the kind described does not, however, permit moulding ofblanks with undercut parts which prevent removal of the blanks from thedies solely by axial displacement inside the dies. For instance, with adevice of this kind it is impossible to mould blanks having a necked-inmiddle part. A device of this kind also does not allow moulding oftwisted or warped blanks, warped blanks having at least one part whereineach section perpendicular to the central axis of the piece is equal tothe preceding one but is rotated through a certain angle relative to thesame.

The prior art also shows devices for moulding blanks of plasticsmaterial, particularly of thermoplastic material, by means of which itis possible to obtain pieces of highly complicated shape. Such devicesessentially comprise at least one die whose surface is equal to that ofthe blank to be obtained and inside which one or more punches ofsuitable shape are disposed. The molten thermoplastic material isinjected (by injection moulding) inside the die and then removed fromthe same upon solidification. In order to allow removal of the blankfrom the die, the die normally comprises a number of parts which can bedisplaced relative to each other, both in the direction of the axis ofthe blank and in the direction perpendicular thereto.

However, the devices of the kind described above only permit moulding ofblanks by injection of molten thermoplastic material inside thecorresponding die; these pieces are fully finished when they are removedfrom saiddie. Therefore, this technique is quite different from that towhich the device in accordance with the present invention relates. Infact, in the device of this invention the compaction of powderedmaterial provides a semifinished blank having the shape of the finishedpiece, but which must be subjected to other processing steps subsequentto removal of the semifinished blank from the device.

SUMMARY OF THE INVENTION The purpose of the present invention is toprovide a device for moulding blanks to be sintered by compaction ofpowdered material, so as to allow moulding of pieces with undercut partswhich. prevent removal of the pieces from the corresponding dies solelyby the axial displacement of the same inside the dies and, inparticular, moulding of twisted or warped pieces.

According to the present invention, there is provided a device formoulding blanks to be sintered, by compaction of powdered material,comprising two punches movable one towards the other and partiallyinside a die in which a blank is moulded. The die comprises at least twoparts. Means are provided for holding the die parts in contact with oneanother during compaction in correspondence with at least one planewhich is parallel to the direction along which the punches move. Meansfor separating the die parts after compaction are also provided. I I

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described inmore detail, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 shows a perspective view of a blank having a middle part ofdimensions different from those of the end parts,

FIG. 2, shows a cross section of the blank of FIG. I,

taken along line II-II,

FIG. 3 shows a section of the piece illustrated in FIG. 1, taken alongline III-III,

FIG. 4 shows a section of the piece illustrated in FIG. 1, taken alongline IV-IV,

FIG. 5 shows a section of the main parts of a mould ing device embodyingthe invention taken along a diametral plane, at the end of the loadingoperation of powdered material, I

FIG. 6 shows a section of the main parts of the moulding device, at theend of the compaction step of the powdered material,

FIG. 7 is a plan view of some parts of the device of FIG. 6,

FIG. 8 shows partial section of the parts of the device of FIG. 7, takenalong the line VIII-.-VIII,

FIG. 9 shows a section of the main parts of the device during thepreliminary step of removal of the blank FIG. 12 shows a section of someparts of the device at the end of the step of removal of the blank fromthe device.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGS. 1 to 4 there is shown,by way of example, a

blank to be moulded by compression of powdered ma, terial by themoulding device. The blank 1 comprises three cylindrical parts 2, 3 and4 of constant cross section, as seen in FIGS. 2, 3 and 4 respectively;the blank is further provided with an axial hole 5. The blank forms anassembly of three coaxial cams.

The blank 1 could not be formed with known moulding devices, such as,for instance the one described above, by means of which it is onlypossible to form pieces comprising two substantially cylindrical and/orprismatic parts of different cross section, united to each another at aplane perpendicular to the direction of the longitudinal axis of theblank. In fact, since the dimensions of the section of the middle part 3are smaller than those of the sections of the end parts 2 and 4, thepiece 1 cannot be formed by means of a device which only comprises twoor more adjacent dies one or more of which are movable relative to theothers in a direction perpendicular to the planes of union of the parts2, 3 and 4 of the blank 1. In this instance, the end parts 2 and 4 wouldform two undercuts, thereby preventing withdrawal and removal of theblank from the die (or a portion thereof) which forms the intermediatepart 3.

A moulding device embodying the present invention comprises a die 6(FIGS. 5 to 12) composed of two parts 6a and 6b, which are normally heldin contact with each other touching over a vertical meridian plane 7(FIGS. 7 and 8) of the die. The two parts 6a and 6b of the die 6 enclosea recess 8 (FIGS. 5,6,9,l1 and 12) whose surface correspondssubstantially to the outer surface of the blank 1 which is to be formedtherein.

A stationary plate 9, of substantially circular shape, includes a seat11 on whose surface the parts 6a and 6b of the die 6 are positioned.These parts can be displaced, relative to each other, in a directionsubstantially perpendicular to that of the vertical plane 7. Each partof the die has a pair of parallel planar side faces 12 (FIGS. 7, 8 andcooperating with guides 13 which ensure a correct movement of the partsin the aforementioned direction. The guides 13 (FIG. 8) aresubstantially L-shaped and are each provided with an attachment part 14adapted to be secured on the surface of the seat 11, a vertical wall 15,and a tab 16 which overlies the upper surface 17 of a part 6a, 6b of thedie 6.

Each part 6 a and 6 b of the die 6 is further provided with a recess 21(FIGS. 7 and 10), inside which a protruding portion 22 (FIGS. 5, 6, 9,11 and 12) ofa movable plate 23 can enter, this plate being displaceablein the direction of the axis of the device. Each of the protrudingportions is provided with a pair of inclined flat surfaces 24s and 25seach of which forms a different angle with the vertical plane 7 (FIGS. 7and 10) of the two parts 6a and 6b of the die and which are adapted tocooperate with corresponding inclined flat surfaces, 24i and 251'respectively (FIGS. 11 and 12) belonging to the plate 9 and to each ofthe die parts.

Each of the protruding portions 22 is provided, at opposite sides, withtwo slots 26 whose axis is inclined at a small angle relative to thevertical plane 7. These slots 26 are adapted to interact with twocorresponding small rollers 27, each of which is disposed on a sidesurface of the recess 21 (FIGS. 7 and 10) and is rotatable about acorresponding pin 28 fastened to one of the die parts 6a, 6b,respectively.

The plate 23 (FIGS. 5, 6, 9, 11 and 12) is carried by another plate 30(shown in dashed lines), which is movable in the direction of the axisof the device and guided, for instance, by means of a pair of columns orposts, not shown. To drive the plate 30 an oscillating lever 31 can beprovided, which is pivoted to the bedplate of the device (not shown) at32 and a pin 33 of which acts inside a slot 34 provided in the plate 30,whilst another pin 35 of the lever is adapted to interact with a cam 36which is integral with a revolving shaft 37. A helical spring 38 causesthe lever 31 to rotate in an anticlockwise direction. In the positionshown in FIGS. 5 and 6, wherein the flat surface 24s and 25s are incontact with the corresponding surfaces, 24i and 25i respectively (FIGS.11 and 12), there is a slight clearance between the pin 35 and theactive profile of the cam 36.

A pair of compacting punches, namely an upper punch 39 and a lower punch41, is adapted to move in the direction of the axis of the device and topartially slide inside the recess 8 of the die 6. These punches whichhave substantially the same cross section as the respective parts of thedie 6, pass through the holes 42 and 43 (FIGS. 11 and 12) provided inthe movable plate 23 and the stationary plate 9. Preferably, in order toassist the sliding movement of the punches as well as to allow an easyand rapid maintenance of the device, the holes 42 and 43 are not formeddirectly in the plates 23 and 9, but are in two bushings 44 and 45secured to the plates.

The axial movement of each of the punches 39, 41 (FIGS. 5, 6, 9, 11 and12), in the case of the embodiment illustrated, is generated byoscillating levers 46 and 47 pivoted to the bedplate of the device at 48and 49 and provided with slots 50 and 51 cooperating with correspondingpins 52 and 53 which in turn are fastened to plates 54 and 55 which areaxially movable on columns, not shown, and integral with collars of thepunches 56 and 57 respectively. These levers are provided with otherpins 58 and 59 cooperating with the cams 60 and 61 respectively. Thefirst of these cams is integral with the shaft 37, whilst the second isintegral with a shaft 63 which is parallel to the shaft 37 and revolvesin the same direction. Two helical springs 64 and 6S normally hold thepins 58 and 59 in contact with the corresponding cams 60 and 61.

A rod 66 is adapted to slide in an axial hole of the punch 41, whilstthe punch 39 is provided with another hole 67, inside which the rod canslide. The axial movement of the rod 66 relative to the punches 39 and41 is generated by an oscillating lever 69which is pivoted to thebedplate of the device at 69, and is provided with a slot 70 cooperatingwith a pin 71 of a plate 72 which is movable axially and is integralwith a collar 73 of the rod. Another end pin 74 of the lever 68 coactswith a cam 75 which is integral with the shaft 63. A spring 77 normallybiases the pin 74 into contact with the cam 75.

A feed duct 78 connected with a hopper (not shown) containing a suitablepowdered material, is adapted to be displaced above the upper surface ofthe plate 23, so as to feed a predetermined amount of the materialinside the recess 8 of the die 6. A die-pressing plate 80, also movableaxially and driven by the plate 54 through elastic means (not shown), isadapted to exert, during the compaction step, a sufficient force uponthe upper surface of the plate 23, substantially as described in our US.patent application Ser. No. 174,325, filed Aug. 24, I971.

Two pins 81 are arranged to slide inside axial holes provided in theplate 9. For clarity only one of these pins is shown in the drawings.Pins 81 are biased upwardly by helical springs 82. These pins areadapted to be inserted, in a manner to be explainedbelow, into recesses83 provided on the lower surface of each part 60, 6b of the die.

At the start of the working cycle of the device, the plate 23 (FIG. 5)is in the position corresponding to the end of its downward stroke incontact with the stationary plate 9. In this position, the surfaces 24sand 25s of each protruding portion 22 will coact with the correspondingsurfaces 241' and 25i respectively (see FIGS. 11 and 12) of the plate 9and of one of the parts 6a, 6b of the die respectively.

In the position described above, the punches 39 and 41 are in theirend-of-stroke position. The first of the punches leaves the hole 42(FIGS. 11 and 12) in the plate 23 fully free, whereas the second punchengages the hole 43 in the plate 9. The feed duct 78 (FIG. 5) restsabove the plate 23 in such a position as to feed powdered materialinside the recess 8 of the die 6. When a predetermined amount ofmaterial has been fed, sufficient for completely filling the spacedefined by the recess 8, the hole 42, the part of the hole 43 left freeby the punch 41, and the upper face of the latter, the feed duct 78 isremoved.

During the movement described above, the diepressing plate 80 is broughtinto contact with the upper surface of the plate 23 (FIG. 6), so as toapply a sub stantial force to the latter. This force will give rise, incoorespondence with the coupled surfaces 24s, 24i and 25s, 25i, topressures which are substantially normal to said surfaces. Theresultants of these pressures, which act upon each part of die 6a and 6band are directed perpendicularly to the contact plane 7, will urge theparts against one other with substantial pressure, so that they willresist, without displacement, the high pressures originating inside therecess 8 during the sub sequent compacting step of the powderedmaterial.

Then, the shafts 37 and 53 and the corresponding earns 36, 60, 61 and 75therewith are caused to rotate in the direction indicated in thedrawings. On account of the profiles of the cams, during thefirst partof their movement of rotation, while the lever 31 remains stationary,the levers 46 and 47 will be moved so as to displace the punches 39 and41 one towards the other, in order to compact the powdered materialcontained in the recess 8. As can be seen from the profile of the cams60 and 61, the punch 39 is moved first, by bringing the same on the edgeof the plate 23 and therefore closing off the recess 8. Subsequently,the punches 39 and 41 are caused to move substantially simultaneouslyaccording to a velocity law depending on the profile of the cams 60 and61. During the movement of the punches, rod 66 is held stationary. Theposition of the various parts of the device at the end of the compactionstep by which the blank 1 is formed, is as shown in FIG. 6.

Subsequently, the removal step of the blank formed by the device willstart, during which the two parts of the die 6a and 6b, are spacedapart, symmetrically relative to the support plane 7. This is attainedwhen, upon rotation of the cam 36 (FIGS. 9 and the latter will cause thelever 31 to pivot in a clockwise direction and lift the plate 30, andtherefore the plate 23 which is integral therewith, as well as thedie-pressing plate 80.

. protruding portions 22 will apply to the corresponding small rollers27, forces in a direction substantially perpendicular to the side walls,whose components normal to the support plane 7 will space apart theparts of the die, 6a and 6b. While the aforementioned movement is takingplace, the parts, being guided by'the guides 13 (FIGS. 7 and 8) willslide on the bottom of the seat 11 of the plate 9 and the surfaces ofthe recesses 8 in the die parts will thus no longer be in contact withthe blank 1. The position in which the die parts of the device are atthe end of the removal step is shown in FIG. 9. In this position, theparts 60 and 6b of the die will be at the maximum distance from oneanother, and the pins 81 will snap, under the action of thecorresponding springs 82, inside the recesses 83 provided in the bottomwall of each of the parts, thereby resilently locking the same in theaforementioned position.

Upon further upward movement of the plate 23, the slots 26 in theprotruding parts 22 will abandon the small rollers 27, as shownin FIG.11. Simultaneously, on account of the rotational movement of the camwhich drives thelevet 68, the rod 66 will be displaced downwards, untilit reaghes the position shown in FIG. 11. Upon rotation of the cams 60and 61 which drive the levers 46 and 47, the upward. displacement of thetwo punches 39 and 41 will start. The punch 41 will now partially liftthe blank 1 between the parts 6a and 6b of the opened die, until thelower surface of the latter is brought above the plane of said die.Subse quently, the upward stroke of the punch 39 will continue, untileit reaches the position shown in FIG. 12. In this position, the hole 5in the blank 1 is fully released from the rod 66 of the die .6 and cantherefore be easily removed from the device, hand or with any suitabletool.

After removal of the blank 1, ahd when the cams of the device haveaccomplished a complere revolution, the various parts of the same willagain take the relative positions shown in FIG. 5 and, therefore, a newworking cycle of the device can start. The recesses 83are so shapedthat, when the die parts are urged together again by the action of therollers 27 in the slots 26, the pins 81 are cammed back into the plate9.

The device embodying the invention can equally well be utilized formoulding twisted or warped blanks.

Among many possible modifications it may be men tioned that the movementof the punches 39 and 41, as well as that of the plate 30 and the rod66, can be effected by actuation devices differents from those describedand illustrated, elg. by means of hydraulic cylinders.

I claim:

1. A device for moulding blanks to be sintered by compaction of powderedmaterial comprising:

a die of at least two parts inside which said blank is moulded, saidparts being movable between a moulding position in contact with oneanother to define a mould cavity in which powdered material can beplaced and an open position spaced from one another; pair of opposedpunches movable toward one another in a compacting stroke and passingthrough openings in said die to compact said powered mate rial in saidmould cavity, said punches moving along axes parallel to at least oneplane of contact of said die parts with one another,

' means for moving said die parts to said moulding position and forholding said die parts in contact with one another in said mouldingposition during said compacting stroke of said punches, and

means for moving said die parts to said open position at the completionof said compacting stroke of said punches.

2. A device according to claim 1 wherein said planes of contact of saiddie parts with one another are such that the inner surface of said diedefining said mould cavity moves away from or tangent to the surface ofsaid formed blank so as not to interfere with said surface of saidformedblank when said die parts are moved from said moulding position to saidopen position. 7

3. A device according to claim 1 wherein the line of movement of saiddie parts between said moulding position and said open position issubstantially perpendicular to the axes of said punches.

4. A device according to claim 3 wherein said die parts when in saidopen position are spaced outwardly -from each other a distancesufficient to allow said blank to be displaced along the axes of saidpunches without interference from said die parts.

5. A device according to claim 1 wherein one of said punches is movablebeyond said compacting stroke to eject said blank when said die partsare in said open position.

6. A device according to claim 1 wherein said moving holding meanscomprises a plate movable axially relative to said punches and providedwith first inclined planes, said die having second inclined planesengagable by said first inclined planes to wedge said die partstogether, and means for urging said movable plate into engagement withsaid die.

7. A device according to claim 6 wherein said separating means comprisesa plurality of slots in said movable plate inclined with respect to theline of movement of said movable plate, and a plurality of correspondingprojections on said die parts, said slots engaging said projections.

8. A device according to claim 7 wherein said first inclined planes andsaid slots are mounted on extensions attached to said movable plate,said extensions being received during said compacting stroke incorresponding recesses in said die parts.

9. A device ac ci M parts rest upon a stationary plate having, guidemeans for guiding the movement of said die parts between said mouldingposition and said open position.

10. A device according to claim 6 wherein the stroke of said movableplate with respect to said stationary plate is at least equal to theheight of said moulded blank.

asses rding toclaiin 1 wherein said die

1. A device for moulding blanks to be sintered by compaction of powderedmaterial comprising: a die of at least two parts inside which said blankis moulded, said parts being movable between a moulding position incontact with one another to define a mould cavity in which powderedmaterial can be placed and an open position spaced from one another; apair of opposed punches movable toward one another in a compactingstroke and passing through openings in said die to compact said poweredmaterial in said mould cavity, said punches moving along axes parallelto at least one plane of contact of said die parts with one another,means for moving said die parts to said moulding position and forholding said die parts in contact with one another in said mouldingposition during said compacting stroke of said punches, and means formoving said die parts to said open position at the completion of saidcompacting stroke of said punches.
 2. A device according to claim 1wherein said planes of contact of said die parts with one another aresuch that the inner surface of said die defining said mould cavity movesaway from or tangent to the surface of said formed blank so as not tointerfere with said surface of said formed blank when said die parts aremoved from said moulding position to said open position.
 3. A deviceaccording to claim 1 wherein the line of movement of said die partsbetween said moulding position and said open position is substantiallyperpendicular to the axes of said punches.
 4. A device according toclaim 3 wherein said die parts when in said open position are spacedoutwardly from each other a distance sufficient to allow said blank tobe displaced along the axes of said punches without interference fromsaid die parts.
 5. A device according to claim 1 wherein one of saidpunches is movable beyond said compacting stroke to eject said blankwhen said die parts are in said open position.
 6. A device according toclaim 1 wherein said moving holding means comprises a plate movableaxially relative to said punches and provided with first inclinedplanes, said die having second inclined planes engagable by said firstinclined planes to wedge said die parts together, and means for urgingsaid movable plate into engagement with said die.
 7. A device accordingto claim 6 wherein said separating means comprises a plurality of slotsin said movable plate inclined with respect to the line of movement ofsaid movable plate, and a plurality of corresponding projections on saiddie parts, said slots engaging said projections.
 8. A device accordingto claim 7 wherein said first iNclined planes and said slots are mountedon extensions attached to said movable plate, said extensions beingreceived during said compacting stroke in corresponding recesses in saiddie parts.
 9. A Device according to claim 1 wherein said die parts restupon a stationary plate having guide means for guiding the movement ofsaid die parts between said moulding position and said open position.10. A device according to claim 6 wherein the stroke of said movableplate with respect to said stationary plate is at least equal to theheight of said moulded blank.